This invention relates to the repair of cables with an electrically insulating dielectric layer whose integrity needs to be maintained. Such a dielectric layer typically surrounds a high voltage electrical conductor, which itself may surround a packaged optical fibre. Located between the packaged fibre and the high voltage conductor, there may be a strength member constituted for instance by one or more layers of stranded steel. Particularly the invention relates to the repair of such cables in which the dielectric layer is covered by a metal tape layer, a function of which is to provide a measure of protection against localised damage of the surface of the dielectric layer which could otherwise give rise to impaired dielectric strength, for instance as the result of the initiation of a crack in the dielectric. In its turn the metal tape layer is protected by a plastics jacket layer. For some applications such cables are required in long lengths, for instance in lengths of 25 Km. During the manufacture of such lengths, imperfections in the metal tape layer or in its covering plastics jacket layer can occur which leave the underlying dielectric layer intact. In these circumstances, rather than to strip the jacket and tape layers from the whole length of cable before recommencing a complete replacement of these two layers, or scrap the entire cable, it would be preferred to effect a localised repair in which only the defective portion or portions of these layers are removed and then replaced with reinstatement material.